Initial screening for the pharmacodynamic effects of drugs typically involves western analysis and/or immunocytochemical observation of the drug response in a selected number of relevant cell types or biological samples. However, such procedures are labor intensive and provide limited information on only one or two variables that relate to the pharmacodynamic effects of the drug. Moreover, the effects of drug combinations cannot easily be understood by examination of western blots or by viewing a limited number of cells through a microscope. Hence, new procedures are needed that allow analysis of multiple pharmacodynamic markers in multiple cells at once. Such procedures would better reflect the overall response of multiple cell types to the drug(s).
Pharmacodynamic drug effects are also better understood when large number of samples from different people are tested. However, collection, storage and testing of such large numbers of samples can be burdensome, particularly if the samples must be extensively purified or manipulated before the actual test is performed. For example, researchers frequently study the effects of drugs on lymphocytes. However, separation of lymphocytes from whole blood typically is done by Ficoll gradient separation, which requires technical expertise and expensive equipment. Hence, screening procedures are needed that do not require extensive manipulation or purification of samples prior to testing.